spherical magnet

[east]

is there such a thing ? has anyone made such a thing ?

 

if not, what is the theory that explains that it canot be done ?

if yes, where are the 'poles' ?

[Mr Skeptic]

If what you are asking is whether there are magnetic monopoles, the answer is that no they have never been found and are prohibited by maxwell's equations. A magnetic monopole would be a magnet that is, say, north all around.

 

On the other hand, if you take an iron sphere and heat it and allow it to cool in a magnetic field, you will have yourself a spherical magnet. It will still have a north and south pole. Or just look down, the earth is a giant spherical magnet. But again, it must have both a north and a south pole.

[swansont]

But again, it must have both a north and a south pole.

Or several (but equal numbers of each)

[YT2095]

what if you built a 3d shape with all like poles on the Inside of it?

say 6x square based pyramids glued together to make a Cube, where the base is the South pole for instance and the apex of each is the North.

 

it wouldn`t be a true monopole, but for some purposes may be suitable.

[Sisyphus]

what if you built a 3d shape with all like poles on the Inside of it?

say 6x square based pyramids glued together to make a Cube, where the base is the South pole for instance and the apex of each is the North.

 

it wouldn`t be a true monopole, but for some purposes may be suitable.

 

I don't think so. I'm guessing the edges would all end up being north, while the centers of the faces would stay south. The way I think about it (because it's the way Farraday thought about it) is that magnetic field lines are all just continuous loops, which are partially embedded in what we call the "magnet." Every loop must come back and meet the other end. So in that case the lines would be emanating from each side and then curving back towards wherever they can squeeze through. And if there's no space, they'll make one, and parts of the magnets will reverse polarity.

[Klaynos]

what if you built a 3d shape with all like poles on the Inside of it?

say 6x square based pyramids glued together to make a Cube, where the base is the South pole for instance and the apex of each is the North.

 

it wouldn`t be a true monopole, but for some purposes may be suitable.

 

You couldn't build it you would get a mess of polls on the surfaces when you force it all together.

[YT2095]

you Could build it, there`s nothing preventing it at all!

but it would be easier if it was Hollow, and say made out of Bar magnets (yes I have stuck 2 like poles together and made a double ended North, bar magnet).

you could extend this to a 3D shape.

 

give me a reason it can`t be done and that I didn`t do what I did.

[the tree]

On a related point, what of a circle where the exterior would be one pole and the interior the other? If the field lines found a route off of the plane that the circle was one, would it hold?

 

If so, I guess that could be called a sort of 2-d pseudo-monopole

[Sisyphus]

you Could build it, there`s nothing preventing it at all!

but it would be easier if it was Hollow, and say made out of Bar magnets (yes I have stuck 2 like poles together and made a double ended North, bar magnet).

you could extend this to a 3D shape.

 

give me a reason it can`t be done and that I didn`t do what I did.

 

See post #5. It works with sticking two bar magnets together because the field lines have somewhere to go. Specifically, they emanate from the ends and curve back towards the middle. This is easy to see with iron filings. If you made it into a 3D shape, however, it wouldn't work.

 

On a related point, what of a circle where the exterior would be one pole and the interior the other? If the field lines found a route off of the plane that the circle was one, would it hold?

 

If so, I guess that could be called a sort of 2-d pseudo-monopole

 

Yes, I'm sure that would work.

[YT2095]

You could be right about the solid version, but a hollow one, I`m not so sure, anyway, I was addressing this bit mainly;

 

You couldn't build it you would get a mess of polls on the surfaces when you force it all together.

[Mr Skeptic]

what if you built a 3d shape with all like poles on the Inside of it?

say 6x square based pyramids glued together to make a Cube, where the base is the South pole for instance and the apex of each is the North.

 

it wouldn`t be a true monopole, but for some purposes may be suitable.

 

Nope, it wouldn't work out. If you did it perfectly you would end up with a non-magnetic 3D shape. More likely, you would end up with a bunch of north and south poles all over the surface

 

http://en.wikipedia.org/wiki/Gauss%27s_law_for_magnetism

 

It does help to think of magnetic field lines as loops that must leave from the north pole and enter at the south pole. No matter how you arrange it, you can't make the loops become straight lines radiating away from a surface.

[Klaynos]

You could be right about the solid version, but a hollow one, I`m not so sure, anyway, I was addressing this bit mainly;

 

By "you couldn't build it" what I meant was you couldn't build it and keep the polls in the same locations. You'd get it splitting into domains all over the place around the edges where the magnets are touching.

 

Bar magnets is trivial compared to this the polls are still there, it's still two bar magnets with some funny buisness with veyr very sharp field lines near the middle as you'd see if you did the bit of paper on top and some iron fillings....

[east]

so far all arguments have been on the basis that the magnet is as it is, with no extra energy input into the system, pyramids, spheres, whatever.

 

given an unstable arragement of magnets but with a little energy persuade it to stay, perhaps a spherical magnet is possible, a monopoled one.

 

what if, we reverse the situation and have all magnets around and pointing to an iron sphere. would not that sphere be a monopole magnetised sphere ?

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Merged post follows:

Consecutive posts merged

(yes I have stuck 2 like poles together and made a double ended North, bar magnet).

you could extend this to a 3D shape.

 

probably a strong glue to hold it all together, but yes, that would be a spherical magnet equivalent. if the magnets are relatively small ( in rod diameter ), the approximation gets better.

 

i am not sure what the resulting forces would be other than the obvious pole-pole repel, but it would be most intersting to 'see' the irong filing pattern just outside the surface. maybe we see a manetism equivalent of surface tension.

 

extending the logic a bit, is we were to assume all the magnetic effects were to cancel out at the surface, that leaves just the ones emanating from the magnet outwards. so a cloud of non mangetic layer followed by high magetic layer just above.

Edited March 11, 2009 by east
Consecutive posts merged.

[Mr Skeptic]

so far all arguments have been on the basis that the magnet is as it is, with no extra energy input into the system, pyramids, spheres, whatever.

 

given an unstable arragement of magnets but with a little energy persuade it to stay, perhaps a spherical magnet is possible, a monopoled one.

 

what if, we reverse the situation and have all magnets around and pointing to an iron sphere. would not that sphere be a monopole magnetised sphere ?

 

No, we are saying you can't make a magnetic monopole because it goes against the laws of physics.

[east]

oh, ok, thanks.

[alan2here]

One could imagine creating a perfect feromagnetic or paramagnetic solid sphere that was hollow and had a lot of space inside in proportan to it's solid outside. Attempting to magnitise it pefectly with north inside and south outside would result in no effect in the same way that getting two equally strong people to have a tug of war nomatter how strong the people would have no effect. Magnitising it inperfectly would presumably result in some valid collection of poles on the inside and outside.

[tvp45]

A very practical way to see this is to try experiments with electromagnets, which are much easier to control. For example, you can take a long rod of iron and put identical two coils in the middle, each facing an opposite direction. You will quickly see that you can get two reasonably identical poles on the ends that are much weaker than what you have with a single coil. As you control leakage, the end poles approach zero. If you use a high mu rod and curve it back into an almost closed "C", with the ends only a few mm apart, the pole strengths will be vanishingly small.

 

You can do the same thing with the spherical case (if you have a spare Magdeburg Sphere lying about), putting small electromagnets on the inside, all oriented out. At first, you'll get a mixture of N and S poles (One more concentrated than the other). To the extent you can make very tiny identical electromagnets, you'll begin to get overlapping N and S and you can imagine the field going to zero in your mind at least.

[Mr Skeptic]

Another thing you can consider is doing the sphere thing with equal but opposite electric charges. Get an insulating sphere, then coat both the outside and the inside with a conductor. Place an electric charge of q on the inside, and -q on the outside. What charge does it look like the sphere has? None! On the other hand, if you put both charges on opposite ends of a rod, you'd get an electric dipole, which would have an electric field that looks very much like a magnetic field (except close to where the charges are). Of course, with electricity you do have electric monopoles, which is why you can separately put the charges on the sphere or rod. If you were to put more of one charge on the sphere, it would act like an electric monopole. But you can't put more of one magnetic pole than the other, because you can't separate one pole from the other.

[Jerry M]

I know this is a bit late, like years, but I've been wondering about this, too.

So, back to the OP's second question, which was never answered that I saw.  Has anyone actually built one?  If not, why not?  Isn't one of the purposes of experimentation to check whether what we expect to happen really does happen?  I would think it would be relatively straightforward, if not necessarily simple to do a first approximation, possibly enough to see if Maxwell has the last word or not.  Alas, I don't have the youth, money, math, machining skills, or knowledge of magnetism to pursue this, but if I did, I'd start with perhaps steel as the material of choice since we don't need or want a super strong magnet for the experiment and steel would be easy to work with.    I'd make it of multiple components; in short a geodesic sphere. 

If you would, imagine a geodesic sphere inside a larger geodesic sphere and in alignment with it.  If you imagine it as a skeletal structure then it is easy to see that the planes that connect the skeleton of the outside sphere's structural components to the matching ones on the inside sphere would define the shapes of the individual components of our magnet.  They would then be magnetized with one pole on the surface of the smaller sphere and the other pole on the surface of the outer sphere, and then glued together, perhaps with superglue, to form the magnetic sphere.  Control of the individual parts would be a bit challenging since they would try to squirm out of position.  Of course the individual components could be designed to go all the way to the center of the sphere, but I would imagine it would be easier to make it hollow.  The higher the frequency of the geodesic, the better your control of the the magnetism of the individual components, but that could get out of hand real fast for the number of individual components involved.

So, what would really happen, without guessing or resorting to unproven theories?  Would the lines "force" their way through to make multiple poles?  Would the whole field just collapse, and if so would the components resume their magnetic properties if it was disassembled or would the field collapse be permanent?  Would you actually have a single pole surface that radiated its lines out into space?  if this is what would occur, then what is happening inside might be the most interesting of all.  Might make a dandy plasma containment field.  Imagine, if you are at the center of the sphere, then every direction is North.  Or South.  Who knows, maybe it would even trigger a Big Bang in a different dimension.  Just kidding.  I think.

No matter what happens, except total field collapse, of course, this would likely be a very interesting toy to play with.  Has it been done?  Anyone want to try?  I'm hoping for some totally unexpected result that redefines physics, but that's just me.

Thanks for taking the time to read this silly proposal!

Jerry

[Bender]

On 10-2-2018 at 5:52 PM, Jerry M said:

So, what would really happen, without guessing or resorting to unproven theories?

There is no need to guess. Maxwell is an extremely successful theory. So successful, in fact, that it predicted a constant lightspeed which lead to another hugely successful theory (special relativity).

There are theories that predict magnetic monopoles, but they require new, currently unknown, particles. Mundane magnets, in whatever configuration cannot break the very laws they are based on. That's like trying to break Newton's laws by throwing a rock.

[Jerry M]

Thank you for the answer, but what does happen in this instance, then?  I admit to having only a layman's understanding of Maxwell's theory.  Does it predict what happens if you try to build such a magnet as I described?  Do the fields find ways through, resembling something like solar prominences.  Do they move about like the prominces, or do the leaking areas become fixed in certain locations.  Or does the field just collapse and go away.  I'm afraid I don't have the math to follow Maxwell's equations.

Again, thanks for responding.

[Bender]

It depends on the specifics, bit I guess solar prominences is a good image. All magnetic field lines coming out of the sphere would have to go back in at another point.

It would remain stationary, but depending on the magnets used, wear out over time.

[Jerry M]

Thanks!

[Raider5678]

50 minutes ago, Jerry M said:

Thanks!

https://totalelement.com/products/1-2-inch-neodymium-rare-earth-sphere-magnets-n48-4-pack?utm_source=google&utm_medium=cpc&adpos=1o1&scid=scplpM12SPHEREN48-4PK&sc_intid=M12SPHEREN48-4PK&gclid=CjwKCAiAtorUBRBnEiwAfcp_Y5ki8KItlNbedvnMsWI37TYDpsNIAjxz-mWfSJ4HmqTO48ZlvSO-1RoCCnkQAvD_BwE

Not saying you should buy them, but those are round magnets.

[Jerry M]

Hey Raider5678.   Those are not what I had in mind at all, but thanks for the info.